Dosbox has a included IPX connexion (port 213 UDP/TCP) and using IPXSetup.exe (after creating the IPX socket).

Of course, you have to find people having DooM 2 DOS and Dosbox, and organizing parties in order to play MP.

At least, that's what we did for the latest DooM 2 cooperative records we got with JCD.

If you want simplicity, use one of these modern ports :

Zdaemon : Most populated port, and we are hosting parties (ie BaseQ). Plus, every night has a event (ours are the FCT , the Frenchies' Chaotic Tuesdays, which is quite a success). Tries to keep the original DooM aspect while adding competitive stuffs.

Zandronum : (Successor to Skulltag) The most "New School" port. Has ZDooM 2.X.X updates, lots of NS mods. Unfortunately, that port suffers from the Quake 3 Arena syndrome, and lost the original Doom's feeling. Plus, has a horrible netcode.

Odamex : The true contestant of Zdaemon. Is completely open-source (code completely clean), with lots of netcode optimisations. But empty as hell (except for the IDL).

As for what kind of Doom...I've grown really tired of all the mods and mods of mods and mods of mods of mods made for Doom. Some old-fashion vanilla survival would be fun. Maybe spice it with NIGHTMARE mode.